The Universe Through the Looking Glass

Sept.
7, 2007: A whole new world came to life for Alice
when she passed through the looking glass – beetles with bad
attitudes, Tweedledee and Tweedledum, smiling cats, talking
tiger lilies and much more.

Mirrors
have special powers in the real world too, especially in the
hands of an astronomer. In fact, modern astronomy depends
on mirrors. Almost every telescope uses a mirror, sometimes
several mirrors, to gather and guide starlight toward some
super-sensitive digital detector where a breathtaking image
can be formed. Without mirrors, it would be almost impossible
to study the universe.

Right:
Astronomers examine the 2.4-meter mirror at the heart of the
Hubble Space Telescope. [More]

For
an X-ray astronomer, it's a little more complicated. "The
X-ray light we use to study the Universe is so energetic,
it would pass right through an ordinary mirror," laments
Brian Ramsey of the Marshall Space Flight Center.

So
Ramsey and colleagues have built an extraordinary sideways
mirror that can harvest high-energy X-rays (also called "hard"
X-rays)." It's called a grazing incidence mirror,"
explains Ramsey, who is HERO's lead scientist, "and it
can guide very energetic X-rays."

Ramsey's
team recently tested the device nicknamed HERO (short for
High Energy Replicated Optics) on-board a balloon launched
from Fort Sumner, New Mexico. The balloon carried HERO above
99% of Earth's atmosphere where it could gather X-rays from
space. The data are being analyzed and results will be available
soon; the team looks forward to some new cosmic images in
never-before-seen detail.

Above: HERO heads for the stratosphere.

The
HERO team is one of many scientific groups that ask the Columbia
Scientific Balloon Facility experts at Fort Sumner to launch
payloads via these enormous balloons. At full inflation, HERO's
balloon is 500 feet wide and rises 1000 feet above the payload.
The balloon facility crew inflates and launches the balloons,
tracks them, and recovers them. Because of the favorable wind
conditions (little or no wind, that is) in May and September,
Fort Sumner is an excellent location for ballooning at those
times.

"People
come out to watch and ask questions," says Ramsey. "One
little boy asked me if our huge telescope had ever landed
on a cow." (No!) Ramsey
added that the Fort Sumner residents are very friendly and
helpful. "They even put on barbecues for us from time
to time," he says. Ramsey is used to hospitality – Southern
hospitality, since Marshall Space Flight Center is in Huntsville,
Alabama.

HERO's
optics, designed and built in Huntsville, include 96 tube-like
"grazing incidence" mirrors nested like the layers
of an onion.

Right:
Like stones skipping across the surface of a pond, X-rays
glance off the sides of grazing incidence mirrors. [More]

Why
the strange shape? Because high-energy X-rays would pass right
through the kind of flat mirror we look in each morning over
our toothpaste. To keep these high-energy photons from passing
through, the mirrors must be angled almost sideways such that
X-ray photons glance off the sides. From there, the photons
travel down the
tubes to detectors that form an image.

When
these mirrors eventually make it to space, they will gather
photons from some of the most violent objects in the Universe:
exploding stars, colliding galaxies and black holes, just
to name a few. The inner violence of these objects is what
makes their photons so energetic and why astronomers need
a high-energy X-ray telescope to study them.

Right:
Three of HERO's tube-shaped X-ray mirror shells (right) and
a nested grouping of mirrors within one cylindrical tube (left).
[Larger image]

The
HERO team had to climb a slippery slope to loft their innovative
optics upward. Their first several attempts failed – each
for a different reason. The
weather was the worst obstacle.

"We
have daily weather briefings," says Ramsey. "When
they say 'the weather is unsuitable for launch through next
Wednesday,' you consider the prospect of yet another week
or two in your motel room. And there are only two restaurants
around, which you get tired of. And your spirits sink a little."

Add to poor weather a few technical difficulties causing aborted
flight attempts, and you get some frustrated scientists.

If
ballooning is so difficult and unpredictable, why does this
team rely on a balloon to give their experiment wings? Ramsey
says the benefits outweigh the difficulties. "A balloon
mission costs much less than a satellite mission, about 1
million as opposed to 100 million and up," he explains.
"The true beauty of ballooning lies in the fact that
the payloads can be reused, and the turnaround time is fast.
After landing via parachute, the team makes any repairs needed
for the payload and prepares it to fly again within a year.
Also, because of its short duration, a balloon mission provides
a great training opportunity for a college student doing research
for a thesis or dissertation."

And
what of HERO's future? Ramsey hopes it is headed for the sunny
skies of the southern hemisphere – Australia to be exact.
The HERO team has submitted a proposal for their payload to
fly from there a year from now.

“Australia
is an interesting place for us to fly because the galactic
center is clearly visible from there. The galactic center
is the most active part of our galaxy. It has lots of [hard
X-ray] sources packed in there, and with our optics we will
be able to resolve those into individual sources and capture
images no one has captured to date.”

Meanwhile,
a big white balloon drifts by, high in the New Mexican sky,
dangling a telescope filled with mirrors that bring a whole
new world to life. In Alice's words, "It's got, oh! Such
beautiful things in it!"